Novel Integrative Genetic Elements of Mycoplasmas

描述(申请人提供)：虽然水平基因转移通过 质粒和噬菌体长期以来一直被认为是在 细菌种群，直到最近才有了移动染色体的贡献 要素得到了充分的实现。大的染色体“岛”赋予 已经描述了致病、共生或代谢特征，其中一些 可以在细菌之间结合。还存在其他重要的集成要素 术语Constin被用来描述那些有配偶关系的人 可自传递的集成元件。关于它们的分布的研究 不同的元素，它们交换遗传信息的能力和它们的 通过整体转移离散基因来改变生物体表型的可能性 基因功能，仍然处于相对的婴儿期。一些CONSTIN集成了 特定于站点；其他站点在选择插入时受到的限制较少 地点。后者可能会深刻影响染色体的结构和动态， 并通过伴随着乱交的突变变化来调节基因功能 整合。最近，在两个不同的Constin类分子中发现了 致病性支原体、发酵支原体和绵羊支原体。这两种元素有共同之处 特征包括接合类基因的存在，侧翼直接 重复和一种非复制的染色体外染色体形式。重要的是，大多数基因都在 这些不寻常的元素缺乏可识别的同源物和编码一种 不存在可识别的DNA整合酶。这是意料之中的 因此，一种“新的”酶实现了这种整合/切除功能。 支原体通常在慢性疾病期间长时间占据宿主的生态位 在不同脊椎动物中的感染，因此可能是重要的 这种“新奇”元素的蓄水池。这强调了有必要理解 这些元素在支原体染色体和支原体染色体中的动态 种群内流动基因库交换的背景。 因此，本提案的具体目标旨在：(一)评估 绵羊分枝杆菌在寄主相关菌株中的分布和基因组环境 支原体；(Ii)检验该元素确实能够 染色体整合，以及(Iii)探索可能的DNA-蛋白质相互作用 在元素的终结点内，因为这些元素被预测将扮演关键的 在移动性中的角色。完成这些目标将增加我们对 这些新颖元素的功能，并将提供一个平台，从 长期目标，了解其内部或内部的能力 种间基因转移，它们对观察到的可塑性的贡献 支原体基因组及其在发病机制中的可能作用可以被探索。

DESCRIPTION (provided by applicant): Although horizontal gene transfer by plasmids and bacteriophages has long been known to disseminate key traits among bacterial populations, only recently has the contribution of mobile chromosomal elements been fully realized. Large chromosomal "islands" that confer pathogenic, symbiotic or metabolic traits have been described, some of which can be conjugated between bacteria. Other important integrated elements exist and the term CONSTIN has been proposed to describe those that are conjugal self-transmissible integrating elements. Studies of the distribution of these diverse elements, their ability to exchange genetic information and their potential to alter the phenotype of an organism by en bloc transfer of discrete gene functions, are still in their relative infancy. Some CONSTINs integrate site-specifically; others are less restricted in their choice of insertion site. The latter may profoundly influence chromosome structure and dynamics, and modulate gene function via mutational changes accompanying promiscuous integration. Recently, distinctive CONSTIN-like elements were identified in two pathogenic mycoplasmas, M. fermentans and M. capricolum. The two elements share features including the presence of conjugation-like genes, flanking direct repeats and a non-replicative extrachromosomal form. Importantly, most genes on these unusual elements lack recognizable homologs and a gene encoding a recognizable DNA integration enzyme is not present. It is anticipated therefore, that a "novel" enzyme performs this integration/excision function. Mycoplasmas typically occupy host niches for long periods during chronic infections in diverse vertebrates, and therefore may serve as important reservoirs for this "novel" element. This underscores the need to understand the dynamics of these elements both within chromosomes of mycoplasmas and in the context of the exchange of mobile gene pools within a population. Accordingly, the specific aims of this proposal are designed (i) to assess the distribution and genomic context of the M. capricolum element in host-related mycoplasmas; (ii) to test the hypothesis that the element is indeed capable of chromosomal integration, and (iii) to explore possible DNA-protein interactions within the termini of the element, as these are predicted to play a critical role in mobility. Completion of these goals will increase our understanding of the function of these novel elements and will provide a platform from which the long term objectives, of understanding their capacity for intra- or inter-species gene transfer, their contribution to the observed plasticity of mycoplasma genomes and their possible role in pathogenesis, can be explored.